Cadmium-zinc-telluride (CZT) arrays with photon-counting and energy-resolving capabilities are widely proposed for next-generation X-ray imaging systems. This work presents the performance of a 2Ã¢...mm-thick CZT pixel detector, with pixel pitches of 500 and 250Ã¢...Î¼m, dc coupled to a fast and low-noise ASIC (PIXIE ASIC), characterized only by the preamplifier stage. A custom 16-channel digital readout electronics was used, able to digitize and process continuously the signals from each output ASIC channel. The digital system performs on-line fast pulse shape and height analysis, with a low dead-time and reasonable energy resolution at both low and high fluxes. The spectroscopic response of the system to photon energies below (109Cd source) and above (241Am source) the K-shell absorption energy of the CZT material was investigated, with particular attention to the mitigation of charge sharing and pile-up. The detector allows high bias voltage operation (>5000Ã¢...VÃ¢...cm-1) and good energy resolution at moderate cooling (3.5% and 5% FWHM at 59.5Ã¢...keV for the 500 and 250Ã¢...Î¼m arrays, respectively) by using fast pulse shaping with a low dead-time (300Ã¢...ns). Charge-sharing investigations were performed using a fine time coincidence analysis (TCA), with very short coincidence time windows up to 10Ã¢...ns. For the 500Ã¢...Î¼m pitch array (250Ã¢...Î¼m pitch array), sharing percentages of 36% (52%) and 60% (82%) at 22.1 and 59.5Ã¢...keV, respectively, were measured. The potential of the pulse shape analysis technique for charge-sharing detection for corner/border pixels and at high rate conditions (250Ã¢...kcpsÃ¢...pixel-1), where the TCA fails, is also shown. Measurements demonstrated that significant amounts of charge are lost for interactions occurring in the volume of the inter-pixel gap. This charge loss must be accounted for in the correction of shared events. These activities are within the framework of an international collaboration on the development of energy-resolved photon-counting systems for high-flux energy-resolved X-ray imaging (1-140Ã¢...keV).This work presents the performance of a 2Ã¢...mm-thick CZT pixel detector, with pixel pitches of 500 and 250Ã¢...Î¼m coupled to a custom 16-channel digital readout electronics, performing on-line fast pulse shape and height analysis. Charge-sharing investigations were performed, at both low and high fluxes, using fine time coincidence analysis and pulse shape analysis.
|Numero di pagine||15|
|Rivista||Journal of Synchrotron Radiation|
|Stato di pubblicazione||Published - 2018|
All Science Journal Classification (ASJC) codes